Biplob Kumar Biswas

Removal and recovery of phosphorus from water by means of adsorption onto orange waste gel loaded with zirconium

Orange waste, an available biomass, was immobilized with zirconium(IV) to investigate its feasibility for phosphate removal from an aquatic environment. Kinetics, effects of pH and foreign anions, and the adsorption isotherm for phosphate have been examined. The adsorption capacity has been compared to that of two commercially available adsorbents such as zirconium ferrite and MUROMAC XMC 3614. The prepared gel was an effective adsorption gel for phosphate removal with a reasonably high sorption capacity of 57mg-P/g, which was four times higher than that of zirconium ferrite. The highest removal of phosphate was observed at low pH, whereas higher pH suppressed phosphate removal, but even up to pH 9 more than 85% phosphate removal was observed. Adsorbed phosphate was eluted by NaOH solution. Fixed bed column-mode experiments confirmed the complete adsorption of phosphate in continuous-mode operation. Throughout the operating conditions, zirconium was not leaked.

Effective removal and recovery of antimony using metal-loaded saponified orange waste.

Zr(IV) and Fe(III) ions were loaded onto an orange waste precursor to prepare a metal-loaded orange waste gel, which was investigated for the adsorptive removal and recovery of antimony (III and V) from an aqueous environment. The loading capacity of the orange waste for Zr(IV) and Fe(III) was found to be 1.40 and 1.87 mmol/g, respectively. The maximum batch mode sorption capacity of the Zr(III)-loaded saponified orange waste (SOW) gel was found to be 0.94 mmol/g for Sb(III) and 1.19 mmol/g for Sb(V). A nearly similar result was found for the Fe(III)-loaded SOW gel with the sorption capacity for Sb(III) and Sb(V) being 1.12 and 1.19 mmol/g, respectively. The presence of a variety of anionic species such as carbonate, chloride, nitrate and sulfate had no influence on the adsorption of both Sb(III) and Sb(V). A column adsorption-elution test demonstrated the utility of this system in continuous mode. Selective sulfide precipitation of antimony is one of the major findings in the present work, which clearly suggests a means of effective recovery of antimony from solution containing antimony and other metal ions. Due to their low cost, availability and significantly high adsorption capacity, the metal-loaded gels are expected to be effectively employed for the removal and recovery of antimony from aqueous solution, thus leading to the establishment of a greener environment.

Leaching of phosphorus from incinerated sewage sludge ash by means of acid extraction followed by adsorption on orange waste gel.

Ashes from sewage sludge incineration have a high phosphorus content, approximately 8% (W/W), which indicates a potential resource of the limiting nutrient. Incineration of sewage sludge with subsequent recovery of phosphorus is a relatively new sludge treatment technique. In this article, the leaching of phosphorus by using sulfuric acid as well as hydrochloric acid by means of several batch experiments was presented. At the same time a selective recovery of phosphorus by adsorption was also discussed. The effects of acid concentration, temperature and time on extraction were studied. The phosphorus leaching increased with the increase in acid concentration and temperature. Kinetic studies showed that the complete leaching of phosphorus took place in less than 4 h. Selective adsorption of phosphorus by using orange waste gel provided a hint for recovery of this natural resource, which eventually could meet the ever-increasing requirement for phosphorus. The overall results indicated that the incinerated sewage sludge ash can be treated with acid to efficiently recover phosphorus and thus can be considered a potentially renewable source of phosphorus.

Selective adsorption of molybdenum(VI) from Mo-Re bearing effluent by chemically modified astringent persimmon.

Astringent persimmon was chemically cross-linked by formaldehyde to obtain a novel kind of adsorption gel, which was named as APF gel. The adsorption behaviors of Mo(VI) and Re(VII) along with other coexisting metals onto the APF gel were studied in the present paper. The APF gel was found to be effective for the adsorption of Mo(VI) while the gel is almost completely inert toward rhenium and calcium over the whole hydrochloric acid concentration region. The APF gel has a low affinity for iron, copper, lead, nickel, manganese and zinc ions when the concentration of HCl is higher than 1 mol/L. The gel exhibited selectivity only for Mo(VI) with a remarkably high adsorption capacity 1.05 mol/kg, and the adsorption behavior obeys the Langmuir model. According to the thermodynamic and kinetic studies, the endothermic adsorption process followed pseudo-second order kinetics. Also, its excellent adsorption characteristics for Mo(VI) were confirmed by the adsorption and elution tests using a column packed with the APF gel. The result provides a new approach for the recovery of Mo(VI) from a industrial waste effluent.

Investigation on the removal of Mo(VI) from Mo-Re containing wastewater by chemically modified persimmon residua.

Persimmon waste was chemically modified by crosslinking with concentrated sulfuric acid to obtain a novel kind of adsorption gel, which was termed as crosslinked persimmon tannin (CPT), hereinafter. The adsorption behaviors of Mo(VI) with other coexisting metal ions onto the CPT gel were investigated. The gel exhibited selectivity only for Mo(VI) ions evidenced by the high value of separation factor of molybdenum and rhenium (β(Mo/Re)=164.37), and the adsorption mechanism of Mo(VI) as a multispecies was studied. The molybdenum adsorption behavior conforms to the Langmuir model with a remarkably high adsorption capacity of 0.56 mol/kg. A kinetic study for the adsorption of molybdenum at various temperatures confirmed that the endothermic adsorption process followed pseudo-second order kinetics. Moreover, its excellent adsorption properties and applicability for Mo(VI) were demonstrated by the removal and separation of Mo(VI) from different Mo-Re containing industrial wastewaters.

Effective Removal of Arsenic with Lanthanum(III)- and Cerium(III)-loaded Orange Waste Gels

Abstract Orange waste has been chemically modified and loaded with lanthanum(III) and/or cerium(III) to examine its adsorption behavior to both As(V) and As(III). Arsenate removal was found to be favored over a pH range of 6 ∼ 9.5 while arsenite removal took place at pH values ranging from 9 to 11. The maximum sorption capacity of the gel for As(III) removal was evaluated as 43 mg/g, while that for As(V) was 42 mg/g. Column-mode tests using the La(III)-loaded gel confirmed a complete removal of As(V). A reasonably high adsorption potential within the design criteria makes the present gel an alternative choice for arsenic removal.

Adsorption Behavior of Fluoride Ions on Zirconium(IV)-Loaded Orange Waste Gel from Aqueous Solution

Adsorption of fluoride was studied batch wise from aqueous solution by using zirconium(IV)-loaded orange waste gel to achieve practical utility and evaluate the viability of the adsorption gel. Fluoride adsorption was found to be dependent on solution pH and the maximum adsorption of fluoride was observed at pH 2–4. The maximum sorption capacity of the gel for fluoride was evaluated as 1.2 mmol/g, which was compared to that of zirconium(IV)-loaded Amberlite 200CT, a strongly acidic cation exchange resin, which was only 0.5 mmol/g in applied experimental condition. The influence of high concentration of co-existing anions on adsorption of fluoride was studied to evaluate selectivity and competitiveness of fluoride adsorption. The presence of foreign anions such as Cl−, , , and had no significant effect on fluoride adsorption of the present gel. Adsorption of fluoride from actual waste plating solution was also carried out, suggesting very effective adsorption at a solid/liquid ratio greater than 4 g/dm3. Repeated use of the gel was also successfully examined over ten cycles of adsorption-elution-regeneration without any degradation of the gel. These results suggest that the modified orange waste gel is a promising candidate for fluoride adsorption from aqueous solution.

Optimization of an adsorption process for tetrafluoroborate removal by zirconium (IV)-loaded orange waste gel from aqueous solution.

This investigation provides new insights into the effective removal of tetrafluoroborate by means of bio-sorption on waste generated in the orange juice industry. It was undertaken to evaluate the feasibility of zirconium(IV)-loaded saponified orange waste gel for removal from an aqueous solution. Batch adsorption experiments were carried out to study the influence of various factors such as pH, presence of competing anions, contact time, initial concentration and temperature on the adsorption of . The optimum removal was observed in the equilibrium pH region 2–3. The presence of co-existing anions showed no adverse effect on removal except . The equilibrium data at different temperatures were reasonably interpreted by the Langmuir adsorption isotherm and the maximum adsorption capacities were evaluated as 2.65, 3.28, 3.87 and 4.77 mmol g−1 at 293, 298, 303 and 313 K, respectively. Thermodynamic parameters such as Δ G°, Δ H° and Δ S° indicated that the nature of adsorption is spontaneous and endothermic. The results obtained from this study demonstrate the potential usability of orange waste after juicing as a good selective adsorbent.

Construction and Evaluation of Rainwater Harvesting System for Domestic Use in a Remote and Rural Area of Khulna, Bangladesh

Scarcity of pure drinking water during the dry season (November–March) is a major problem in Bangladesh, which needs to be addressed. This crisis has been further aggravated due to surging populations. Rainwater can provide some of the cleanest naturally occurring water and can hold a great potential in dealing with the current challenge of acute arsenic poisoning as well as physical water scarcity in many parts of Bangladesh. In this connection, rainwater harvesting (RWH) system has been constructed in a very remote and rural village in Khulna, Bangladesh, for a 4-membered household. It consists of a concrete catchment of 40 m2 area, a supporting and collection system made of PVC pipes, and two locally available plastic storage tanks having capacity of 2000 L each. The study also investigates the quality aspects of the stored rainwater, which include measurement of pH, alkalinity, hardness, total dissolved solids (TDS), iron, chloride, nitrate, and turbidity, using standard methods. The results showed that not only the quality of harvested rainwater is good but also the amount of water is enough for a 4-membered household to meet its domestic use throughout the year.

Biosorbents for Removing Hazardous Metals and Metalloids

Biosorbents for remediating aquatic environmental media polluted with hazardous heavy metals and metalloids such as Pb(II), Cr(VI), Sb(III and V), and As(III and V) were prepared from lignin waste, orange and apple juice residues, seaweed and persimmon and grape wastes using simple and cheap methods. A lignophenol gel such as lignocatechol gel was prepared by immobilizing the catechol functional groups onto lignin from sawdust, while lignosulfonate gel was prepared directly from waste liquor generated during pulp production. These gels effectively removed Pb(II). Orange and apple juice residues, which are rich in pectic acid, were easily converted using alkali (e.g., calcium hydroxide) into biosorbents that effectively removed Pb(II). These materials also effectively removed Sb(III and V) and As(III and V) when these were preloaded with multi-valent metal ions such as Zr(IV) and Fe(III). Similar biosorbents were prepared from seaweed waste, which is rich in alginic acid. Other biosorbents, which effectively removed Cr(VI), were prepared by simply treating persimmon and grape wastes with concentrated sulfuric acid.